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International Journal of Bioprinting Bioprint micro breast cancer

Scheme 1. The direct volumetric drop-on-demand (DVDOD) bioprinting process for engineering micro-cancer tissues. (A) DVDOD mechanism, with
red spheres indicating the placement of bioink droplets. Adapted from Grottkau et al. (B) Representative photo of a bioprinter. Adapted from Grottkau
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et al. (C-i and C-ii) The initial placement of a bioink droplet (symbolized in red) containing cancer cells onto the Petri dish. (C-iii and C-iv) Subsequent
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placement of a second bioink droplet (symbolized in green), which contains a mixture of human umbilical vein endothelial cells (HUVECs) and fibroblast
cells, onto the Petri dish. The second droplet is dispensed under a higher pressure to merge it with the first. This collision-like action incurs both spatial
separation and integration of the three cell types involved following the merging of the two droplets.
units. Significantly, varying outcomes can be achieved by hydrogels. Initially, using a designated dispenser, this
dispensing the same droplet volume under different drive bioink was deposited on a Petri dish surface, forming the
pressures, which can be used to generate droplet collisions primary droplet (Scheme 1C-i and C-ii). Subsequently,
to generate features within a droplet. 14 droplets holding the medium and a fibroblast–HUVEC
mixture were released onto this primary droplet with
The open-source GRBL control system, which increased pressure via a secondary dispenser (Scheme
incorporates GRBL firmware, Arduino boards, and motor 1C-iii and C-iv).
controllers, governs the multi-linear actuator movements,
covering the XYZ gantry and the syringe plunger motions. To simulate cancer nests, the primary and relatively
Activation of the pulsed air is streamlined via GRBL’s in- extensive homogeneous droplet containing cancer cells
built on-off control feature. Standard GRBL-backed G- was fragmented into multiple smaller cellular clusters.
and M-codes direct the bioprinter’s motion and pulsed air As the high-pressure droplets collided with the initial
toggling. These codes are relayed to the bioprinter through droplet, they acted as disruptive forces. These forces
GRBL-compatible code senders. Moreover, a pressure compartmentalized the concentrated cancer cells into
regulator maintains consistent pulsed air pressure. clusters, while enabling their merger into a larger droplet
on the substrate. Notably, the fibroblasts and HUVECs
2.5. Bioprinting process surrounded and partially infiltrated these cancer cell
A specialized bioink was formulated by amalgamating clusters. Rapid solidification of the bioink was triggered by
specific cancer cells (either SUM149, MDA-MB-231, thrombin, stabilizing the created cellular structures, and
or MCF-7) with a matrix of collagen type I and fibrin preventing inter-cluster interfaces.

Volume 10 Issue 3 (2024) 560 doi: 10.36922/ijb.2911